Multiple exposure pathway proposal for
Cr+6 and Cr+3announced by the
Department

Sept. 18, 1998

Multiple exposure pathway proposal modified
to reflect September 3, 1998 changes by the United States
Environmental Protection Agency (USEPA) in the Integrated
Risk Information System (IRIS) database

Initially the Department used a 100 milligram
total chromium per kilogram of dry weight soil (mg total
Cr/kg DW soil, equivalent to parts per million or ppm) action
level prior to 1989. This action level was based on a multiple
of the maximum New Jersey background total chromium soil
concentrations derived from Rutgers University data and
also took into account qualitative toxicological information.

The Department established subsequent guidance
on a chromium cleanup level in 1989 with a value of 75 mg
total Cr/kg DW soil to preclude allergic contact dermatitis
(ACD) in more than 10 percent of a sensitized population.
This number was based on the work of Bagdon (1989) and a
risk assessment conducted for the Department by Environmental
Science and Engineering, Inc. (NJDEP, 1989). Its initial
application was site-specific for the chromate production
waste contaminated sites in Hudson County. It is important
to note that the USEPA does not use the ACD endpoint as
a basis for determining the need to remediate a site.

The Department developed this guidance
on the basis of a 10 milligrams of hexavalent chromium per
kilogram of dry weight soil (mg Cr+6/kg DW soil)
cleanup level. However, the lack in confidence of a hexavalent
chromium (Cr+6) analytical method for soil caused
the Department to rely on the use of total chromium data.
Based on an analysis of the available data (NJDEP, 1989),
the Department estimated that the 95 percentile of the sample
distribution of the ratio between Cr+6 and total
chromium in chromate ore waste residue was 0.14. Consequently,
the target level of 75 mg total Cr/kg DW soil was not expected
to result in a Cr+6 level greater than 10 mg
Cr+6/kg DW soil in soil samples. Eventually this
action level supplanted the earlier 100 mg total Cr/kg DW
soil value for use statewide.

In 1993 the Department further refined
the earlier guidance and began using the values of 10 mg
Cr+6/kg DW soil and 500 milligrams of trivalent
chromium per kilogram of dry weight soil (mg Cr+3/kg
DW soil). The endpoint was ACD and based on the work of
Bagdon and Hazen (1991). The Department's Division of Science
and Research indicated that a 10 milligram Cr+6
per liter solution (mg Cr+6/l) would cause ACD
in 10 percent of a sensitized population. Making a conservative
assumption that all the Cr+6 was extractable,
the Division of Science and Research determined that this
was equivalent to 10 mg Cr+6/kg DW soil. The
500 mg Cr+3/kg DW soil number was based on information
in Bagdon and Hazen (1991) that trivalent chromium (Cr+3)
was less potent than Cr+6 by a factor of 50 relative
to ACD. This guidance was in place until September 3, 1998.

Concurrent with this change was a shift
in the Department's position on measuring hexavalent chromium
directly. As a result of Department investigations, modifications
in the analytical methodology were made. This along with
greater experience in using the methodology increased the
Department's confidence in measuring Cr+6 concentrations
in soil directly. Consequently, the Department determined
that the use of total chromium as a surrogate was no longer
necessary.

Subsequent research, discussions with the
responsible parties and other stakeholders, and the impact
of recent legislation (Hazardous Discharge Site Remediation
Act, N.J.S.A. 58:10B) have led the Department to consider
changing the minimum elicitation threshold (MET) for ACD
from 10 to 25 mg Cr+6/l. The Department has now
completed it's evaluation of the human health study conducted
by ChemRisk - - McLaren/Hart and James Nethercott, M.D.
(1995), and the Department formally proposes to use 25 mg
Cr+6/l as the MET.

Another development is that the Department
no longer considers the conservative assumption of 100%
extractability as necessarily appropriate based on its experience
with chromium contamination and in particular the solid
chromate production waste found in Hudson County. The Department
intends to institute a protocol that will assess the extractability
and therefore availability of Cr+6 in a fluid
media. The specifics of the protocol are described below.

In response to information requests from
the regulated community, the Department developed several
draft basis and background documents to communicate the
Department's current thinking on the chromium issues. The
Department held an informal interested party review (IIPR)
of these same documents in September 1995. As part of this
outreach effort, a series of public meetings were held.
These included meetings held at St. Aedan's School and St.
Michael's Methodist Church in Jersey City. A meeting with
interested environmental groups was also held as well as
a meeting with the Hudson County chromium responsible parties
(AlliedSignal, Inc.; PPG Industries, Inc.; and representatives
of Occidental Chemical Corporation). The large response
(from 12 separate entities totaling approximately 1,000
pages of written comments) generated by this IIPR caused
the Department to further investigate many of the aspects
of the chromium issues and in many cases revise the Department's
original position. This document constitutes in part the
Department's response to those comments.

In the past, much of the Department's attention
has appeared to focus on the ACD endpoint. This is because
the Department believed that the ACD related cleanup criterion
would dictate where it was necessary to remediate. However,
with the adjustment for extractability, it is likely that
other human health endpoints such as cancer (air inhalation
pathway) may determine the remediation goal. Of course ecological,
ground water, and surface water impacts must also be evaluated
when determining if remediation is required.